Human plasma contains a superfamily of serine proteinase inhibitors, the serpins, which are glycoproteins of Mr = 40,000- 60,000. Members of the serpin family participate in regulation of blood clotting, the complement system, and they protect tissues from proteinases released by blood cells. Deficiencies or mutations of serpins in humans leads to several hereditary diseases. We have identified a protein in the hemolymph of an insect, the tobacco hornworm Manduca sexta, which is a member of the serpin family of proteinase inhibitors and have determined its amino acid sequence from the sequence of its clones cDNA. Specific aims of this proposal are 1) purification and characterization of serpins from insect hemolymph; 2) isolation and sequencing of cDNA clones for members of the serpin gene family from M. sexta and from Drosophila melanogaster; 3) isolation and sequencing of serpin genes from M. sexta and Drosophila melanogaster; 4) identification of physiological functions of insect serpins; 5) study of the hormonal regulation of insect serpin gene expression. The study of insect serpins may yield valuable basic information as a non- vertebrate model for serpin biochemistry and molecular biology, and it may provide targets for novel methods of insect control. Furthermore, the study of insect serpin genes will generate new information on regulation of insect genes during development.